With the advances in circuit and system design, the complexity of electronic circuits, such as the number of integrated devices, has continued to increase. The increased integration has led to smaller devices, increased functionality, smaller device size, and lower cost per unit size or area.
To further increase circuit or device density, sometimes electronic circuits or devices are arranged in a three-dimensional (3D) configuration, or are stacked. By stacking devices, the footprint of the resulting device shrinks. Also, stacking devices may decrease the overall interconnect lengths. Less interconnect length in turn may result in faster signal propagation, less susceptibility to noise, lower power dissipation, etc. In addition, stacking devices in a 3D configuration allows “mixing and matching” devices that perform different functionality, use different technologies, etc.